This invention relates generally to plant irrigation systems and more particularly, but not by way of limitation, to a system for irrigating potted plants from below.
Overhead irrigation of various plants grown in containers out-of-doors is extremely wasteful of water. Published estimates suggest that in excess of 80% of the water pumped does not reach the container, but falls between the containers or on aisles, walkways or roads adjacent the container production area. In areas of winds and low humidity, estimates suggest that as much as 40% of the water discharged by a sprinkler above-ground is lost to evaporation. Losses may be even greater with rapidly turning sprinklers that create very small water droplets, thus increasing the droplet surface area subject to evaporation.
Attempts to water various plants grown in containers with small tubes (1/8 to 1/4 inch in diameter) for individual containers have proven satisfactory for plants on level greenhouse benches. By watering only the growth medium (soil mix) in the container and not the foliage of the plant, many disease problems are reduced or eliminated and the volume of water pumped and carried through the plumbing system is much smaller than with overhead sprinkler irrigation since only the container volume is wetted. Attempts to use this system out-of-doors, however, have generally been unsuccessful for several reasons: (a) rodents (e.g., rats, rabbits and land turtles) repeatedly bite off the small watering tubes; (b) working among the small tubes and containers (such as for pruning, spraying, applying fertilizers, etc.) is awkward; and (c) if a tube is cut by a rodent or pulled from a container by an employee of the plant nursery, generally the plant dies before the problem is noticed.
Attempts to adapt various drip irrigation systems for watering plants grown out-of-doors in containers have also been unsuccessful. These systems generally use plastic pipe about 1/2-inch in diameter. This eliminates the rodent problem that occurs with smaller tubes; however, the awkward working conditions for employees is increased since a tube must remain over the center of the top of a series or row of containers. Unlike the smaller tubes whose ends are fastened to the growth medium in the container, these larger pipes over the tops of the containers are impractical to fasten to the top of the container or stem of the plant. Polyethylene is the plastic used most, if not exclusively, for this pipe system because of its cost and durability; however, polyethylene undergoes considerable expansion and contraction when heated and cooled. If the drip emitters in the 1/2-inch drip irrigation pipe on top of the container are positioned over the center of the container for most effective water application to the plant when the pipe is hot, the emitters will be poorly positioned when the water is turned on and the pipe is cooled and contracts. Likewise, if the pipe and emitters are positioned properly when the pipe is cool, when the water is turned off and the pipe heats on a sunny day, the expansion forces the emitters out of proper position. In some cases, the pipe is forced off the side of the container by the expansion. Unless the position of the pipe is checked and repositioned frequently, thereby using much labor, many plants are lost or injured before the problem is corrected.
Researchers and individuals in the business of growing plants in containers out-of-doors in New Zealand and England have devised sand capillary beds that water plants from below. The water rises from the moist sand into the growth medium by the adhesive forces (attraction of water by particle surfaces) and cohesive forces (attraction of water molecule for water molecule) involved in capillary movement. On a small scale and under the mild climatic conditions of New Zealand and England, this watering system works reasonably well; however, shortcomings of this system include: (a) cost of construction; (b) maintenance and periodic replacement of the sand; (c) transplant shock arising from roots which grow out the drain holes of the containers and into the sand; (d) increased water loss from the surface of the sand capillary bed (which can increase water usage to as much as overhead sprinklers) when environmental conditions are appropriate (e.g., low humidity, wind and high temperature); (e) germination of weed seed and growth of weeds on the wet surface between containers; and (f) algae growth which can quickly become unsightly and limit the useful life of the sand.
Capillary mats are used in the greenhouse and florist industries. These are continuous mats of fabric or foam rubber material. An entire mat is wetted--much like the capillary sand beds--and water moves via capillarity up into containers placed on the mat. These mats, regardless of composition, are subject to the same shortcomings as the sand beds.
In view of the foregoing, there is the need for a new type of watering system for plants, particularly those grown out-of-doors, which properly irrigates the plants but which does not exhibit the aforementioned shortcomings.